1. Field of the Invention
The present invention relates to a control apparatus of an internal combustion engine mounted to a motor vehicle or the like, and more particularly to a control apparatus of an internal combustion engine which can be preferably applied to a requirement of reducing an engine torque and can execute a combustion at a dilute air fuel ratio.
2. Description of the Prior Art
In recent years, in an internal combustion engine mounted to a vehicle or the like, in view of problems such as an environmental problem, a reduction of fuel consumption and the like, an attention is paid to a lean burn cylinder injection of fuel type internal combustion engine which burns by increasing an air fuel ratio so as to make a fuel dilute. Further, in the lean burn cylinder injection of fuel type internal combustion engine mounted to the vehicle or the like as mentioned above, there is a case that an output reduction control is required in the internal combustion engine for a gear change time at which an operating state of the vehicle is changed, and there have been proposed various kinds of control apparatuses of the internal combustion engine executing a combustion control suitable for the requirement.
For example, a control apparatus of a cylinder injection of fuel type internal combustion engine described in JP-A-2000-120481 is structured such as to reduce a fuel injection amount and make an air fuel ratio lean, thereby restricting an output property of the internal combustion engine in the case that the internal combustion engine is in a compression lean mode state at a time when an output reduction requirement is applied, and to reduce the fuel injection amount and delay an ignition timing, thereby restricting the output property of the internal combustion engine in the case that it is in a non-compression lean mode state.
Further, a control apparatus of an internal combustion engine described in JP-A-10-61476 is structured such that in the internal combustion engine capable of burning at a dilute air fuel ratio by stratifying a fuel supplied to a combustion chamber, the control apparatus controlling the combustion thereof can rapidly and with an improved response reduce an engine torque in correspondence to a requirement of reducing the engine torque by synchronously compensating (phase lag controlling) a fuel injection timing and an ignition timing, when the requirement of reducing the engine torque is applied.
Further, a control apparatus of an internal combustion engine described in JP-A-11-324748 is provided with a torque control means for executing a fuel cut of an optional cylinder so as to limit a number of operating cylinders at a time when an output torque down of the internal combustion engine is required, compensating so as to increase an amount of fuel supplied to the operating cylinders, thereby compensating an air fuel ratio of an air-fuel mixture to a rich side, preventing the air-fuel ratio from becoming equal to or more than a predetermined value, and increasing and reducing various kinds of control amount (the ignition timing or the like) for controlling an operation state of the internal combustion engine so that an actual output torque becomes a required torque.
In this case, in the method of changing the torque by making the air-fuel ratio lean such as the control apparatus of the internal combustion engine as described in JP-A-2000-120481, in the case of intending to improve a specific fuel consumption by the dilute air-fuel mixture combustion, the air fuel ratio is set to a lean state near a combustion stabilization limit, as shown in FIG. 11. At this time, when reducing the fuel supply amount so as to make lean, for the purpose of reducing the torque, it is over the combustion stabilization limit, so that the combustion is deteriorated, further a misfire is sometimes generated, and there is a case that a deterioration of driving property and exhaust gas is generated. Further, in the case of making the air fuel ratio lean so as not to be over the combustion stabilization limit by taking this into consideration, there is generated a problem that a margin for making lean is not sufficient and the torque can not be changed to the required engine torque in some cases.
Further, the control apparatus of the internal combustion engine described in JP-A-10-61476 is structured such as to reduce the engine torque by controlling the ignition timing and the injection timing by way of the phase lag, however, in the control mentioned above, as is different from the matter that the combustion on the basis of a theoretical air fuel ratio has a feature that an ignition timing changing range is wide as shown in FIG. 13A, a compatible range between the ignition timing and the injection timing capable of obtaining the stable combustion is narrow at a time of a dilute combustion time (particularly at a stratified combustion time) as shown in FIG. 13B. Accordingly, in the case of deflecting from the range, the deterioration of the combustion and by extension the misfire are sometimes generated in the same manner, so that a problem that the driving property and the exhaust gas are deteriorated is generated. Further, in the case of making so as not to deflect from the compatible range with taking this into consideration, there is a case that the margin for the phase lag of the ignition timing and the injection timing is not sufficient and the torque can not be changed to the required engine torque.
Further, the control apparatus of the internal combustion engine described in JP-A-11-324748 is structured such as to execute the fuel cut of the optional cylinder so as to limit the number of the operating cylinders at a time when the output torque down of the internal combustion engine is required, however, is structured such as to compensate so as to increase the amount of the fuel supplied to the operating cylinders, thereby compensating the air fuel ratio of the air-fuel mixture to the rich side, for the purpose of restricting an emission deterioration at the same time of the fuel cut of the cylinder, and to prevent the air fuel ratio from becoming equal to or more than the predetermined value for the purpose of restricting the misfire of the operating cylinders by compensating the air fuel ratio to the rich side, so that there is a problem that an accurate torque control of the internal combustion engine can not be executed in the dilute combustion state at the required torque value.